Since the earliest stages of development of electronic timepieces, a ripple-down counting system using binary flip-flops has been used in the counter circuit. However, now many supplemental functions are required in addition to the basic primary function of keeping time. It is difficult to include many functions both primary and supplemental into an electronic timepiece using a conventional ripple-down dividing system. More recent circuits for electronic timepieces include the use of shift registers to supplement the basic divider system because many functions can be provided by using the shift register.
Many solid state electronic timepieces use liquid crystals with extremely small current consumption for their display. Because the liquid crystal is not self-illuminating, a lamp or an illuminating device is required in order to properly read the display in poorly-lit environments. However, because the resistance of the lamp is not large as compared with the internal resistance of the battery source, the supply voltage is appreciably lowered when lighting of the lamp is initiated. This condition is especially aggravated at low temperatures.
In a conventional ripple-down dividing system, because of its static operation, the contents of the system are not influenced by a drop in the supply voltage of a magnitude which would seriously affect the performance of a shift register. Where a shift register is used, there is a strong possibility of significant disordering of the contents of the register. Disturbance of performance due to a drop in the supply voltage may affect the dynamic operation of the shift register itself or that of the clock which controls the operation of the shift register.
What is needed is an electronic timepiece which combines supplemental functions, which load down the power supply source and diminish its voltage, on an non-interfering basis with primary functions requiring a high level of voltage for reliable performance.